Millen started 17 of the 20 games he appeared in for the Huskies, throwing for 2,657 yards and winning the Orange Bowl in January 1985 as a junior, in the infamous "Sooner Schooner" game. The win propelled 11-1 Washington to the #2 national ranking, behind unbeaten and untested[1]Brigham Young University. Coming in as a walk-on transfer, Millen beat out Chris Chandler for the starting job.[2] Chandler later became the Huskies starting quarterback and went on a successful NFL career.

Selected by Los Angeles Rams in the third round of the 1986 NFL Draft, Millen missed his entire rookie season with the Rams in 1986 after fracturing an ankle and landing on injured reserve for the entire season. Millen missed most of the 1987 season with a back injury and only had one pass attempt for the season.[2] By this time, Jim Everett – who the Rams had traded for with the Houston Oilers after being the #3 pick in the 1986 NFL Draft – had become entrenched as the Rams starter, and Millen would soon be heading out the door.

After being released by the Rams, Atlanta picked him up off waivers, and he ended up playing in three games for the Falcons in 1988, throwing for 215 yards on the year. The following season, he played in five games – with one start - and completed 62% of his passes for 432 yards. In 1990, he started two games for the Falcons – winning both – completing 54% of his throws for 427 yards.[2]

Millen signed with the New England Patriots on April 1, 1991, as a Plan B free agent.[2] In the fourth week of 1991 season, Millen replaced Tommy Hodson as the starting quarterback for the Patriots. Millen's record as the starter was 5-7, and the Patriots overall record for that year was 6-10; a vast improvement from their 1-15 record from a season ago.

For the season, Millen threw for 3,073 yards with 9 touchdown passes and 18 interceptions. It marked only the fifth time in team history that a quarterback had thrown for 3,000 yards in a season. Millen had several notable performances that season, starting off with his first start against the Houston Oilers where he led New England to a 24-20 upset win by completing 22 of 33 passes for 244 yards and a 34-yard game-winning touchdown strike to Greg McMurtry with 34 seconds left in the game. He had his first career 300-yard passing performance against Minnesota on October 22 – when he was 22 out of 32 for 326 yards and a touchdown pass.[2]

He was named player of the game two consecutive weeks in November when he completed 20 out of 26 passes for 257 yards and a touchdown pass against Miami, then completed 30 passes for 372 yards and a touchdown throw the following week against the Jets. The next week, he scored his first touchdown rushing, with a one-yard sneak in a 16-13 win against Buffalo. Then on December 8 – he completed 21 of 40 passes for 330 yards for two touchdowns, including a 45 yard game winning strike to WR Michael Timpson in overtime against Indianapolis.[2]

During the 1992 season, Millen shared quarterback duties with three others; Tommy Hodson, Scott Zolak, and Jeff Carlson. He led all Patriot quarterbacks with 1,203 passing yards and eight touchdown passes, but New England's final record was a miserable 2-14. Millen suffered a third degree separated shoulder on the seventh play of the season.[3]

The Patriots 2-14 record led to a complete overhaul of the team and franchise in 1993. Millen was traded to Dallas and with the #1 overall pick in the 1993 Draft, New England selected Washington State QB Drew Bledsoe.

Millen was traded to the Super Bowl champion Dallas Cowboys in June 1993 as insurance for injured starter Troy Aikman, who had just undergone surgery for a herniated disk. Steve Beuerlein – the backup quarterback from the previous year – had signed with the Phoenix Cardinals as a free agent. Aikman was expected to miss six to 12 weeks at the time, as he rehabbed from his surgery, while Millen and Jason Garrett would fill the void in the meantime. Millen himself had separated his left shoulder three times during the previous season.[4]

As it turned out, Millen never did attempt a pass in the regular season, as Aikman healed well from his injury, and eventually the Cowboys signed Bernie Kosar as their third quarterback – along with Aikman and Garrett – after Kosar had been released by the Cleveland Browns midway during the 1993 season.

Millen would play his final two years in the NFL as a backup to John Elway in Denver during 1994 and 1995. He played in eight games for the Broncos, starting twice, and throwing for 1090 yards with three touchdown passes and a 63% completion percentage.[5]